THIS “Hydarium” of Northamptonshire is found in a Peterborough Cartulary (Cott. MS. Vesp. E. 22, fo. 94 et sq.). It is drawn up hundred by hundred, like the surveys of Leicestershire and of Lindsey, and is, therefore, probably connected with the assessment of Danegeld. Although it is of special value for reconstituting the Domesday Vills, the assessment it records so often varies from that which is found in Domesday that we cannot institute a close comparison. The introduction of a “parva virgata” further complicates the reckoning. That the original document was written on a roll is shown by the use of the phrase “per alium rotulum.” The statement on fo. 97b that there ought, at one place, to be half a hide more “per rotulos Wyncestrfie[ie],” would seem to refer to Domesday; but on the next page we read:–

Since Domesday records this holding as “v. hid. et una virgata terræ,” the reference (if the text of the survey is right) must clearly be to some other record preserved in the national treasury.